This invention relates to the ablation of atherosclerotic plaques in human patients using lasers.
Such ablation has been carried out using a variety of lasers, e.g., argon lasers, at various wavelengths, e.g., 514 nm (for argon lasers). The technique typically involves the use of a flexible optical fiber associated with the laser, as described, e.g., in Choy U.S. Pat. No. 4,207,874, hereby incorporated by reference. In known techniques, the plaque is first visualized, either by angiography or using a coherent fiber optic bundle built into the laser catheter, and the ablating laser is then aimed and "fired" at the plaque.
There have been some attempts to improve selectivity in the absorption of laser light by plaques, compared to surrounding tissues, by selectively staining the plaque with, e.g., hematoporphyrin (Spears et al. (1983) J. Clin Invest. 71, 39-399). Hematoporphyrin is a photosensitizing agent which, when exposed to laser light, may bring about the photochemical destruction of the plaque.